Regarding the spelling EID.
, not EDIBUS
as the post says), I think there is some evidence that spelling was more conservative in the late Republican period than our manuscripts and editions would indicate (e.g. Quintilian's statement about the use of geminate s
in Cicero's time (caussa
) which is completely unattested in our manuscripts). Even beyond that, inscriptions and coins tended to conserve archaic spellings more than other texts, and EI
for long I
is pretty common in inscriptions.
Here's an interesting coin from the Augustan age commemorating an old treaty with Gabii (foedus p.r. qum Gabinis
), where "cum" is spelled "qum". Though, as a professor of a friend of mine pointed out, this is less likely to indicate a genuine spelling and more a deliberate attempt at archaism, like saying "ye olde treatie" in English.